In general, mechanical or electromechanical actuators are used to apply a stimulus to a device in order to switch its function between or among functional states. The required actuation may depend on the characteristics of the device being switched. For example, a device may be able to hold its state without further assistance from the actuator. In another example, the device may require actuator assistance to hold its state. Actuators may simply make electrical connections or they may apply a required mechanical force. The latter actuators may work using any phenomenon that generates or transmits a force; wherein the force can be applied actively or passively. Such forces include hydraulic, pneumatic, electric, electrostatic, electromagnetic, thermal, such as might be encountered in materials having shape memory, and mechanical forces. Such forces may be converted into motion.
Actuators may provide unstable states of operation that require the supply of energy to hold one state or another in actuation. However, in applications where it is desirable to conserve energy, such as in devices that use batteries, it is often desirable to for an actuator to provide one or more stable states. In such actuators, little or no energy input is required to hold a state in, for example, “engaged” or “disengaged” positions. Moreover, actuators may have more than two states of operation when, for example, they are used to switch among different states of a device.
In certain circumstances it may be desirable for an actuator to switch between or among states using minimal energy, hold its state without further expenditure of energy, and apply mechanical forces characteristic of each state to the device being actuated. For example, such a device may be desirable for actuating a clutch with a high mechanical advantage.
Various attempts have been made to provide such an actuator. For example, U.S. Pat. No. 8,702,133 to Sun et al provides an actuator for an electronic door lock that includes “a stationary first magnet assembly, a beam, and a second magnet assembly,” wherein the first magnet “includes at least one magnet stationarily positioned within the electronic door lock. The beam is movable relative to the first magnet assembly to a first position and a second position. The second magnet assembly is connected to the beam and is configured to be magnetically repulsed away from the first magnet assembly. The repulsion of the second magnet assembly maintains the beam in either the first or second position until the beam is selectively actuated therefrom.” However, in this configuration, the forces applied in each of the two states are symmetrical such that the magnet on the movable beam is “magnetically repulsed” about equally in both states of actuation. Many devices to be actuated, such as, for example, clutches with high mechanical advantage, require a “pull” in one state and a “push” in the other state, without drawing power from a power source when in either state. Therefore, there remains a need for actuators having the characteristics hereinabove described. The present application for patent discloses an actuator that addresses these needs.